How to set a JTable column as String and sort as Double?

Question

I'm still fairly new to Java and have a question in regards to JTable (more specifically JXTable) and sorting rows by column class with mixed data type... Let me elaborate...

I have a JXTable that holds data for a product listing. This table has a column for price which I have set to String.class only so that I can display a price with a '$' prepended.

The problem I'm having is when the rows are sorted by price, they are not sorted as Doubles, but rather they are sorted as strings so these values:

89.85, 179.70, 299.40, 478.80

are sorted as:

179.70, 299.40, 478.80, 89.85 (Ascending) and 89.85, 478.80, 299.40, 179.70 (Descending)

What I would like to do is remove the '$' at the time of sorting and sort the column as Doubles. How would I accomplish this?

EDIT:

Thank you very much Jiri Patera for your response. It was a great help in helping me to understand that the tablecellrenderer is responsible for manipulating values in these types of situations. Below is the finished excerpt that has finally accomplished what I want.

public Component getTableCellRendererComponent(JTable pTable, Object pValue, boolean pIsSelected, boolean pHasFocus, int pRow, int pColumn) {

        // Use the wrapped renderer
        Component renderedComponent = mWrappedRenderer.getTableCellRendererComponent(pTable, pValue, pIsSelected, pHasFocus, pRow, pColumn);
        Component renderedComponentHeader = pTable.getTableHeader().getDefaultRenderer().getTableCellRendererComponent(pTable, pValue, pIsSelected, pHasFocus, pRow, pColumn);

        if (pColumn == 4 && pValue instanceof Double){
            DecimalFormat df = new DecimalFormat("$###,##0.00");
            Double d = (Double) pValue;
            String s = df.format(d);
            renderedComponent = mWrappedRenderer.getTableCellRendererComponent(pTable, s, pIsSelected, pHasFocus, pRow, pColumn);
        }

        // Set the alignment
        Integer alignment = mSpecialColumnAlignmentMap.get(pColumn);
        Integer width = mSpecialColumnWidthMap.get(pColumn);
        if (alignment != null) {
            ((JLabel) renderedComponent).setHorizontalAlignment(alignment);
            ((JLabel) renderedComponentHeader).setHorizontalAlignment(alignment);
        } else {
            ((JLabel) renderedComponent).setHorizontalAlignment(mDefaultAlignment);
            ((JLabel) renderedComponentHeader).setHorizontalAlignment(mDefaultAlignment);
        }

        if (width != null){
            pTable.getColumnModel().getColumn(pColumn).setPreferredWidth(width);
            pTable.getColumnModel().getColumn(pColumn).setMaxWidth(width);
        }

        return renderedComponent;
    }

As you can see, I already had a custom tablecellrenderer. I used the DecimalFormat to format the price as I want it.

Hope this helps someone else out in the future.

Gracia

Don't make the column class String but rather a numeric type. Instead have the cell renderer use a NumberFormat / currency instance that shows the "$" sign. – Blockage

Answer 1

HFOE is right. However, this may be tricky for a Java newbie. Pardon me for using anonymous inner classes. See the following example to get some hints...

package test;

import java.awt.Component;
import java.util.ArrayList;
import java.util.List;

import javax.swing.JFrame;
import javax.swing.JScrollPane;
import javax.swing.JTable;
import javax.swing.table.AbstractTableModel;
import javax.swing.table.DefaultTableCellRenderer;


public class TableTest {

  public static void main(String[] args) {
    TableTest tt = new TableTest();
    tt.start();
  }

  private void start() {
    JTable t = new JTable(new AbstractTableModel() {
      private static final long serialVersionUID = 1L;
      private List<Double> values = new ArrayList<Double>();
      {
        values.add(Double.valueOf(179.70d));
        values.add(Double.valueOf(299.40d));
        values.add(Double.valueOf(478.80d));
        values.add(Double.valueOf(89.85d));
      }
      @Override
      public String getColumnName(int column) {
        return "Double";
      }
      @Override
      public Class<?> getColumnClass(int column) {
        return Double.class;
      }
      @Override
      public int getRowCount() {
        return values.size();
      }
      @Override
      public int getColumnCount() {
        return 1;
      }
      @Override
      public Object getValueAt(int rowIndex, int columnIndex) {
        return values.get(rowIndex);
      }
    });
    t.setDefaultRenderer(Double.class, new DefaultTableCellRenderer() {
      private static final long serialVersionUID = 1L;
      @Override
      public Component getTableCellRendererComponent(JTable table,
          Object value, boolean isSelected, boolean hasFocus, int row,
          int column) {
        Double d = (Double)value;
        String s = "$" + String.valueOf(d.doubleValue());
        Component c = super.getTableCellRendererComponent(table, s, isSelected, hasFocus,
            row, column);
        return c;
      }
    });
    t.setAutoCreateRowSorter(true);
    JFrame f = new JFrame();
    f.setSize(320, 200);
    f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    JScrollPane sp = new JScrollPane(t);
    f.getContentPane().add(sp);
    f.setVisible(true);
  }

}

Matabele

+1, but.. "Pardon me for using anonymous inner classes." Huh? Is that some of design 'no-no'? As someone who writes a lot of SSCCEs, I often make poor 'design' decisions simply to demonstrate a point in a self-contained code. I would never think to offer apologies for the design, in that case! – Mohn

@AndrewThompson: They're perfectly acceptable for a quick continuation. They just don't scale well; +1 to Jiri for identifying the shortcut in this edge case. I sometimes use a static nested class in an sscce for easy re-factoring. – Crosscountry

Thanks for opinions, guys. I just do not feel right when they are longer than say three lines. I use them in SSCCE only although I know they maybe hard to read for newbies. – Matabele